Separation of concerns - DPC12

Separation of Concerns

Separation of concerns About Joshua  Joshua Thijssen, NoxLogic / Techademy  Freelance Consultant, Developer, Trainer  Development in PHP, Python, Perl, C, Java  jthijssen@noxlogic.nl  @jaytaph

Separation of concerns About Stephan  Stephan Hochdörfer, bitExpert AG  Department Manager Research Labs  enjoying PHP since 1999  S.Hochdoerfer@bitExpert.de  @shochdoerfer

Separation of concerns It is what I sometimes have called the separation of concerns, which [...] is yet the only available technique for effective ordering of ones thoughts. Edsger W. Dijkstra, "On the role of scientific thought" (1974)

Separation of concerns SoC […] is the process of breaking a computer program into distinct features that overlap in functionality as little as possible. http://en.wikipedia.org/wiki/Separation_of_concerns

Separation of concerns It`s all about focusing!

Separation of concerns One step a time. Focus on the details!

Separation of concerns<?php$items = array();$token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token);$feed = json_decode($feed, true);foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); }}$feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident");$feed = json_decode($feed, true);foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]);}foreach($items as $item) { echo $item[message];}

Separation of concerns<?php Controller part!$items = array();$token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token);$feed = json_decode($feed, true);foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); }}$feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident");$feed = json_decode($feed, true);foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]);}foreach($items as $item) { echo $item[message];}}

Separation of concerns<?php$items = array();$token = file_get_contents("https://graph.facebook.com/oauth/access_token?...");$feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token);$feed = json_decode($feed, true);foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); }}$feed = file_get_contents("http://search.twitter.com/search.json?q=from:ident");$feed = json_decode($feed, true);foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]);}foreach($items as $item) { echo $item[message]; View part!}

Separation of concerns Very unstable. Not safe for changes....

Separation of concerns „Make everything as simple as possible...“

Separation of concerns Establish boundaries

Separation of concerns What are the boundaries? Presentation Layer

Separation of concerns What are the boundaries? Presentation Layer Business Layer

Separation of concerns What are the boundaries? Presentation Layer Business Layer Resource Access Layer

Separation of concerns Isolate functionality, break it apart!

Separation of concerns<?phpnamespace AcmeDemoBundleController;use SymfonyBundleFrameworkBundleControllerController;use SensioBundleFrameworkExtraBundleConfigurationRoute;use SensioBundleFrameworkExtraBundleConfigurationTemplate;class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); } }

Separation of concerns $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true); foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]); } return array(items => $items); }}

Separation of concerns Focus on one responsibility a time!

Separation of concerns<?phpnamespace AcmeDemoBundleController;use SymfonyBundleFrameworkBundleControllerController;use SensioBundleFrameworkExtraBundleConfigurationRoute;use SensioBundleFrameworkExtraBundleConfigurationTemplate;class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); Facebook connector $token = file_get_contents("https://graph.facebook.com/oauth/access_to..."); $feed = file_get_contents("https://graph.facebook.com/ident/feed?".$token); $feed = json_decode($feed, true); foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); } }

Separation of concerns Twitter connector $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true); foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]); } return array(items => $items); }}

Separation of concerns Interfaces as a contract

Separation of concerns<?phpinterface ConnectorInterface { /** * Will return an array of the latest posts. * return array */ public function getLatestPosts() { }}

Separation of concerns<?phpclass FacebookConnector implements ConnectorInterface { protected $handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $items = array(); $token = file_get_contents("https://graph.facebook.com/oauth/access..."); $feed = file_get_contents("https://graph.facebook.com/. $this->handle."/feed?".$token); $feed = json_decode($feed, true); foreach($feed[data] as $post) { if(123456789012 === $post[from][id]) { $items[] = array( date => strtotime($post[created_time]), message => $post[message]); } } return $items; }}

Separation of concerns<?phpclass FacebookConnector implements ConnectorInterface { protected $handle; public function __construct($handle) { $this->handle = $handle; } public function getLatestPosts() { $token = $this->getAccessToken(); return $this->readPosts($token); } protected function getAccessToken() { return file_get_contents("https://graph.facebook.com/oauth/access_?..."); } protected function readPosts($token) { // read the post, filter all relevant and return them... }}

Separation of concerns<?phpclass FacebookConnectorV2 extends FacebookConnector { protected function getAccessToken() { return md5($this->handle); }} Easy to extend, will not influence the behaviour of other methods!

Separation of concerns<?phpnamespace AcmeDemoBundleController;use SymfonyBundleFrameworkBundleControllerController;use SensioBundleFrameworkExtraBundleConfigurationRoute;use SensioBundleFrameworkExtraBundleConfigurationTemplate;class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get(FbConnector); $items += $fb->getLatestPosts(); $feed = file_get_contents("http://search.twitter.com/search.json?..."); $feed = json_decode($feed, true); foreach($feed[results] as $tweet) { $items[] = array( date => strtotime($tweet[created_at]), message => $tweet[text]); }

Separation of concerns<?phpnamespace AcmeDemoBundleController;use SymfonyBundleFrameworkBundleControllerController;use SensioBundleFrameworkExtraBundleConfigurationRoute;use SensioBundleFrameworkExtraBundleConfigurationTemplate;class DemoController extends Controller { /** * @Route("/", name="_demo") * @Template() */ public function indexAction() { $items = array(); $fb = $this->get(FbConnector); $items += $fb->getLatestPosts(); $twitter = $this->get(TwitterConnector); $items += $twitter->getLatestPosts(); return array(items => $items); }}

Separation of concerns Will improve the testability!

Separation of concerns Will reduce tight coupling!

Separation of concerns Will increase component reuse!

Separation of concerns The value of separation Why should I do it?

Separation of concerns The value of separation 1. Getting rid of code duplication

Separation of concerns The value of separation 2. Application becomes more stable and easier to understand

Separation of concerns The value of separation 3. Single responsibility offers clear extension points

Separation of concerns The value of separation 4. Increases the reusability of components

Separation of concerns How to separate the concerns?

Separation of concerns How to separate? Horizontal Separation Presentation Layer Business Layer Resource Access Layer

Separation of concerns How to separate? Service Separation Service Interface Layer Business Layer Resource Access Layer

Separation of concerns How to separate? Service Separation Frontend / UI Webservers REST API Solr Search Service Datastore

Separation of concerns How to separate? Vertical Separation Module A Module B Module C

Separation of concerns How to separate? Vertical Separation Presentation Presentation Presentation Layer Layer Layer Business Business Business Layer Layer Layer Resource Resource Resource Access Layer Access Layer Access Layer

Separation of concerns Cross-cutting concerns? How to deal with security or logging aspects?

Separation of concerns How to separate? Aspect Separation Aspects Presentation Layer Business Layer Resource Access Layer

Separation of concerns How to separate? Aspect Separation <?php namespace AcmeProductsAspects; /** * @FLOW3Aspect */ class LoggingAspect { /** * @FLOW3Inject * @var AcmeLoggerLoggerInterface */ protected $logger; /** * @param TYPO3FLOW3AOPJoinPointInterface $joinPoint * @FLOW3Before("method(AcmeProductsModelProduct->delete())") */ public function log(TYPO3FLOW3AOPJoinPointInterface $jp) { $product = $jp->getMethodArgument(product); $this->logger->info(Removing . $product->getName()); } }

Separation of concerns Dependency Direction

Separation of concerns Dependency Direction "High-level modules should not depend on low-level modules. Both should depend on abstractions." Robert C. Martin

Separation of concerns Inverting Concerns Presentation Layer Business Layer Resource Access Layer

Separation of concerns Inverting Concerns Presentation UI Presentation Layer Component Layer Business Business Layer Layer Resource Resource Access Layer Access Layer

Separation of concerns Inverting Concerns The goal of Dependency Injection is to separate the concerns of obtaining the dependencies from the core concerns of a component.

Separation of concerns What are the benefits? Let`s recap....

Separation of concerns What are the benefits? 1. Facilitate reusability

Separation of concerns What are the benefits? 2. Ensure the maintainability

Separation of concerns What are the benefits? 3. Increasing the code quality

Separation of concerns What are the benefits? 4. Enables everyone to understand the application

Separation of concerns What are the benefits? 5. Allows developers to work on components in isolation

Thank you!

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Separation of concerns - DPC12

by Stephan Hochdörfer on Jun 09, 2012

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